Microelectromechanical system (MEMS) devices are devices that operate on a very small scale, typically in a range of tens of microns to a few millimeters. MEMS devices mostly are fabricated using integrated circuits (IC) technology. Production of MEMs devices, likewise, enables one to realize relatively low manufacturing costs because of the batch fabrication techniques and the small size of the devices. In some applications MEMS devices are imperceptible to the unaided human eye. MEMS devices include many different devices used for a variety of purposes. One device in particular is a movable micromirror having the capability of rotating about a pivot point or an axis. One end of the micromirror is coupled to an anchor, which may be a substrate, using a bimorph actuator that may be activated by sending an electrical current to a heating element in the actuator. The current causes the temperature of the actuator in the micromirror to increase, which in turn causes the actuator to bend. While the micromirror may be rotated about a pivot point, the micromirror may not be translated to another position. Instead, the micromirror is fixedly attached to the anchor.
Numerous actuation devices have been used with MEMS devices to achieve vertical displacement. For instance, displacements of between about 7.5 μm and about 50 μm have been achieved through the use of electrostatic vertical comb drives. In addition, electrostatic and electromagnetic actuators have generated displacements of about 6 μm and about 20 μm. However, the displacements of most displacement devices have been limited to these ranges. Thus, a need exists for larger amounts of vertical displacement within MEMS devices.
Many applications exist in which a micromirror having the ability to be moved relative to a Z-axis could be used rather than simply pivoting about an anchor. For instance, axial scanning of an optical coherence tomography (OCT) imaging system requires translational mirrors capable of moving out-of-plane along a z-axis. OCT is an imaging technology that can be used to obtain cross-sectional imaging of biological tissues for noninvasive or minimally invasive medical diagnosis. OCT is based on low coherence interferometery and fiber optic technology, and has very high spatial resolution (<10 μm). OCT has been successfully used to detect various cancers.
Another application that could benefit from a micromirror or microlens movable along a Z-axis is optical coherence microscopy (OCM). OCM has been used to obtain cross-sectional information of biological or biomedical tissues, which is the same as OCT, and is based on low coherence interferometry. However, OCM differs from OCT in that OCM produces higher lateral resolution because it uses a sharply focused laser beam, which in some applications may be about 1 μm. In contrast, OCT requires 1–3 mm focus depth, which limits the laser spot size to about 10 μm. Currently, axial scanning of a reference mirror is accomplished using Plumbum (lead) Zirconate Titanate (PZT) actuators and relies on motorized stages to perform z-scanning and x-y scanning. As a result, the current OCM devices are bulky and slow. Thus, a need exists for a more compact and more time efficient device for enabling z-scanning and x-y scanning.